Racemization of optically active 2-substituted phenyl glycine esters

a phenyl glycine and phenyl glycine technology, applied in the field of racemization of optically active 2substituted phenyl glycine esters, can solve the problems of easy degradation, high cost of discarding this material, and difficult racemization of free amino acids

Inactive Publication Date: 2004-04-15
USV LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Free amino acids are difficult to racemize.
Decomposition is extensive with 2-(2-chlorophenyl) glycine, not only because it is difficult to racemize, but also because it easily degrades.
Discarding of this material is expensive and contributes to total production cost.
It also forms an effluent and increases effluent treatment costs.
From an economic viewpoint, it is wasteful to discard an otherwise useful enantiomer from an enantiomerically enriched mixture, such as mother liquors with unwanted isomers.

Method used

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  • Racemization of optically active 2-substituted phenyl glycine esters
  • Racemization of optically active 2-substituted phenyl glycine esters
  • Racemization of optically active 2-substituted phenyl glycine esters

Examples

Experimental program
Comparison scheme
Effect test

example 2

[0031] Racemization of methyl 2-chlorophenyl glycinate and isolation of liberated racemized ester as free base.

[0032] One hundred kilograms of methyl 2-(2-chlorophenyl glycinate (SOR -85.degree. to +5.degree.) is dissolved in three hundred fifty liters (350 liters) of methanol in a 1000 liter Mild Steel glass lined reactor. This mixture is cooled to 5.degree. C. by circulating chilled water or brine through an external jacket.

[0033] Forty five liters (73.7 kilograms) of thionyl chloride are added to the reaction mixture while stirring and maintaining a temperature of the reaction mixture between 25.degree. C. and 30.degree. C. After completion of the addition, water or brine circulation is stopped and heating of the reaction mixture begins by means of hot water circulation through an external jacket. Heating is continued and reflux is maintained for about twelve hours.

[0034] The methanol is now slowly distilled out while maintaining reduced pressure so as to maintain the temperature...

example 3

[0038] Conversion of methyl 2-(2-chlorophenyl) glycinate to its tartaric acid salt.

[0039] 60 kilograms of (+) tartaric acid (SOR=12.degree. c=20, H.sub.2O ) is dissolved in three hundred fifty liters of methanol in a mild steel glass lined reactor. Methyl 2-(2-chlorophenyl) glycinate obtained by the previous procedure (eighty kilograms) is dissolved in fifty liters of methanol and added to the reaction mixture at once. The reaction mixture is stirred for approximately five minutes and transferred to a high density polyethylene tank. Five grams of pure tartaric acid salt of methyl 2-(2-chlorophenyl) glycinate(SOR=.about.90.degree.) is added as seed. The reaction mass is kept at room temperature for ninety six hours.

[0040] Crystals of (+) tartaric acid salt of methyl-2-(2chlorophenyl) glycinate and separated by centrifugation and dried at 40.degree. C. for eight hours

[0041] Yield: -49-50 kilograms 2 Specific optical rotation [ ] D 20 = 85 .degree. - 93 .degree. ( c = 1 % in methanol )...

example 4

[0042] Isolation of Second Crop:

[0043] The mother liquor of example 3 is transferred to a reactor and the methanol is distilled out under reduced pressure while maintaining the temperature below 60.degree. C. After recovery of approximately 250 liters of methanol, the reaction mass is collected in polyethylene drums and allowed to solidify. The solid mass containing hemitartarate of (-)-methyl 2-(2-chlorophenyl) glycinate as a major product is stored as second crop for future reprocessing. Yield: About 100-120 kg. 3 SOR after drying at 60 .degree. C . [ ] D 20= - 85 .degree. to +5 .degree. ( c = 1 % in methanol )

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Abstract

A process for preparing racemic mixtures containing nearly equal amounts of stereo isomers of compounds of formula (I), or their salts, by heating an enantiomerically enriched material with thionyl chloride. A required useful enantiomer may thereby be recovered from unwanted mother liquors that would otherwise be otherwise be discarded.

Description

BACKGROUND TO THE INVENTION[0001] The present invention pertains to a process for the recovery of enantiomers from unwanted mother liquors using racemic mixtures containing stereoisomers having the structure (I) below, or its salt, by heating an enantiomerically enriched chemical mixture with thionyl chloride. 2[0002] The present invention is also directed to a process for preparing racemic mixtures containing nearly equal amounts of enantiomers of 2-chlorophenyl glycine methyl ester from mother liquors enriched with unwanted isomers, as its hydrochloride salt, by heating the mother liquors with thionyl chloride.DISCUSSION OF RELATED ART[0003] Racemization is generally carried out by heating an acid with or without the presence of an alkali or a solvent. Free amino acids are difficult to racemize. The temperature required for racemization is often in the range of 140.degree.-180.degree. C. and some decomposition occurs at temperatures within this high range.[0004] Decomposition is e...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C07B55/00C07C51/41C07C59/255C07C227/36C07C227/40C07C229/00C07C229/36C07C229/38
CPCC07B2200/07C07C227/36C07C229/36C07B55/00
Inventor MAHESHWARI, KRISHNA K.SARMA, RAYAPROLU KODANDARAMAJOSHI, SHREERANG VIDYADHARBARDE, ANUP RAMKRISHNASUTAR, RAJIV PANDURANGRANADE, PRASAD VASUDEO
Owner USV LTD
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